Patent GB-1032674-A (GB)
Title: Process of catalytic conversion
IPC: C10G65/06
Filed: 1964-01-08
Abstract: A process for the catalytic conversion, e.g. hydrogenation of a charge stock comprising 6 to 60 weight per cent of unsaturated compounds which readily thermally polymerize on indirect heating comprises heating the charge stock to a temperature below the polymerization temperature, admixing a preheated inert material in the form of a liquidor gas which does not adversely react with the components of the charge stock and which will remain substantially undecomposed under the thermal conditions of the conversion, the temperature and amount of added liquid or gas being such as to raise the temperature of the charge stock to that necessary for the catalytic conversion and contacting the admixture with a catalyst mass in a catalytic conversion zone, the said liquid or gas being admixed with the charge stock just prior to contacting the admixture with the catalyst mass.  The charge stock is preferably preheated to 127 DEG  C. and the temperature of the admixture is between 149 DEG and 260 DEG  C.  The admixture is contacted with the catalyst at 177 DEG  to 399 DEG  C.  The unsaturated compounds which thermally polymerize are defined as being any compounds which have a gum value of over 500 m.g. per 100 ml. of the compound after 5 hours according to A.S.T.M. test D-873. Inert materials used, which are preferably preheated to 260 DEG  to 416 DEG  C., boil at 121 DEG  to 454 DEG  C. and include propane, hexane, hexadecane, cyclobutane, cyclooctane, benzene, tetralin and naphthalene and are used in a volume ratio of inert material to charge stock of 0.2:1 to 40:1.  The thermally polymerizable charge stocks comprise unsaturated hydrocarbons having 2 to 20 carbon atoms per molecule, many are mentioned, e.g. methyl acetylene, 2,6 - octadiene, 1 - phenyl - 1,3 - butadiene, 1,3-cyclopentadiene &c., and the preferred charge stocks are catalytically cracked petroleum fractions boiling between 38 DEG  and 371 DEG  C., e.g. debutanized aromatic distillates from cracking of C2 to C4 hydrocarbons.  The charge stocks may also comprise 40 to 94% by weight non-polymerizable diluent compounds, e.g. paraffins, naphthenes, aliphatic and cyclic monoolefins and aromatic compounds not containing vinyl substituents.  Other diluent compounds are mercaptans, disulphides, <PICT:1032674/C4-C5/1> thiophenes, cyclic thioethers, pyrroles, pyridines, phenols and peroxides.  The time between admixing the preheated inert material and contact of the admixture with the catalyst mass is less than 2 minutes and preferably 10 to 60 seconds.  At least 5% by weight, preferably 10 to 80%, of the diluent hydrocarbons in the charge stock and the inert material are maintained in the liquid phase during the conversion process.  In a preferred embodiment of the invention the preheated admixture is contacted at 149 DEG  to 399 DEG  C. at pressures up to 84 kg/cm.2 with hydrogen in presence of at least one of the metals, or oxides or suphides thereof, of Group VI and the iron metals from Group VIII, e.g. Cr, Mo, W, Fe, Co and Ni, preferably supported on alumina, silica or magnesia. As shown, in the Figure, a debutanized aromatic distillate, obtained by cracking and hydrogenating a light hydrocarbon gas, e.g. ethane or propane, is passed through line 40, preheater 42 which heats the charge stock up to a maximum temperature of 127 DEG  C. and line 52 and is mixed with a mixture of hydrogen from recycle line 46 and a straight run distillate fuel oil preheated to above 149 DEG  C. in preheater 48.  The reaction mixture passes into catalytic hydrogenation reactor 54 maintained at 177 DEG  to 399 DEG  C.  The products are cooled in cooler 58 and liquid products are withdrawn from high pressure separator 62 for fractionation.  In a further preferred embodiment a charge stock comprising a monoolefin and at least 6 weight per cent of thermally polymerizable unsaturated compounds but less than that amount of thermally polymerizable unsaturated compounds necessary to increase the temperature of the charge stock due to the hydrogenation of the readily thermally polymerizable unsaturated compounds to efficiently hydrogenate the mono-olefins is hydrogenated by passing through the reactor and injecting a second preheated inert material into the reactor at a point where the hydrogenation of the readily thermally polymerizable unsaturated compounds is complete and further hydrogenating the total reaction mixture to completely hydrogenate the mono-olefin, the amount and temperature of the first inert material being sufficient to increase the temperature of the mixture between 149 DEG  and 249 DEG  C. and to maintain a continuously moving liquid film on the hydrogenation catalyst to reduce polymer formation in the reactor and the amount and temperature of the second inert material being sufficient to increase the temperature of the total reaction mixture to between 266 DEG  and 316 DEG  C.  The second inert material may be passed counter current to the mixture charge stock and first inert material.